At high speed, the hull of a vehicle such as the high-speed craft is known to be acted upon by significant aerodynamic forces. In a number of cases, provided aerodynamic surfaces are incorporated in the hull of the high-speed craft, these forces tend to balance out, partially or fully, the weight of the hull. This pattern of motion allows a noticeable decrease in the specific power of the craft due to its reduced drag.
These effects that are enhanced by the influence of the water surface ("ground") occur at sufficiently high velocities: generally above 10 to 12 Fr.sub.v (which corresponds to 110-120 km/h for a craft of 1000 kg displacement). At such speeds, it involves certain difficulties to provide both longitudinal and lateral stability of the craft, especially when manoeuvring. It is due to the fact, that if sudden perturbations occur such as waves, gusts of wind, the craft may lose contact with water, take off from the surface, and capsize. When manoeuvring at such speeds, the craft is acted upon by significant centrifugal forces which may disturb the lateral stability of the craft and result in capsizing, or else, if the area of the steering surfaces is not sufficient, the craft becomes essentially uncontrollable. These circumstances require a developed tail fin assembly, the optimum configuration of the tail fins for such high-speed craft being either T- or V-shape (N. I. Belayin, "Ekranoplany", 1977, Sudostroenie/Leningrad/, pp. 187-195).
One known high-speed vessel is a ground-effect craft comprising a hull with a T-shaped tail fin assembly, lifting wings with sponsons, an engine with a propulsion unit, and a steering gear (N. I. Belavin, "Ekranoplany", 1977, Sudoestroenie (Leningrad), pp. 96-99; DE, A, 1234539, U.S. Pat. No. 3,190,582). The tail fin assembly of such craft includes a vertical fin with a portion thereof being made rotatable about the vertical axis and connected to the steering gear, and a stabilizer with a pair of straight (zero-V) half-wings, the stabilizer being secured to the stationary portion of the fin.
One disadvantage of this craft is its poor maneuverability when moving over the water surface. It manifests itself in the fact that in order to make a turn of a specified (small) radius, the craft has either to change the travel conditions and to increase the clearance or to substantially reduce the speed and contact the water surface. With increased clearance height, which is in itself an uneconomical and hard-to-control procedure, a heel has to be provided which is inward relative to the turn, this heeling being achieved by means of an additional control system and additional controls, i.e. ailerons (winglets). The additional controls involve great difficulties in steering the craft and, what is more, making the control inefficient when the craft moves at a low height. As a result, even though additional control members are provided, the steering of the craft, when it moves at a low clearance height above the water surface ("ground") is made difficult, because we fail to provide an effective counteraction against the centrifugal forces developed when maneuvering the craft.